[cxx-abi-dev] Missing mangling of elaborated type specifiers

[Richard Smith]

On 20 March 2014 12:04, John McCall <rjmccall at apple.com> wrote:

> On Mar 20, 2014, at 11:16 AM, Hubert Tong <hstong at ca.ibm.com> wrote:
> > John McCall <rjmccall at apple.com> wrote on 20-03-2014 01:56:10 PM:
> > > From: John McCall <rjmccall at apple.com>
> > > To: Hubert Tong/Toronto/IBM at IBMCA,
> > > Cc: cxx-abi-dev at codesourcery.com
> > > Date: 20-03-2014 01:56 PM
> > > Subject: Re: [cxx-abi-dev] Missing mangling of elaborated type
> specifiers
> > >
> > > On Mar 19, 2014, at 9:02 PM, Hubert Tong <hstong at ca.ibm.com> wrote:
> > > > It seems that the ABI is missing mangling for elaborated type
> specifiers.
> > > >
> > > > Background:
> > > > As mentioned in Core Issue 1162, elaborated-type-specifiers may be
> > > used to cause SFINAE.
> > >
> > > Good point.  I guess this should just be added to <unresolved-name>.
> > > Would you care to make a proposal?
> > >
> >
> > Sure.
>
> Great!
>
> I think I was wrong, by the way; you should add it to to the
> <class-enum-type> grammar as a decoration before we enter <name>.


I think we should leave the 'typename' case alone and change the
struct/class/union/enum cases, since the latter cases are much less common.
There seem to be two obvious approaches:

1) Use a prefix indicating that there was a tag keyword, but don't say
which one.
2) Use a prefix indicating which keyword was used

The first approach seems viable -- we can never have a mangling collision
where a type is one of struct-or-class, union, or enum in one TU and a
different one of those three in another TU (and the struct and class cases
are functionally equivalent).

The second approach seems better for demanglers (and taking that argument
to its logical conclusion suggests that we should mangle 'class' and
'struct' differently).

Strawman:

<class-enum-type> ::= <name>    # non-dependent type name or
*typename-specifier*
                  ::= TC <name> # dependent elaborated class type
                  ::= Ts <name> # dependent elaborated struct type
                  ::= Tu <name> # dependent elaborated union type
                  ::= Te <name> # dependent elaborated enum type

Thoughts?
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